Force measuring device



March 18, 1952 LA COSTE ET AL FORCE MEASURING DEVICE 4 Sheets-Sheet 1 Filed Sept. 12, 1946 Inn LUCIEN LaCOSTE ARNOLD ROMBER INVENTORS SEIHAQY 3 we a AMu-U AT ORNEYS Fl'.l

March 18, 1952 LA COSTE ET AL 1 2,539,709

FORCE MEASURING DEVICE Filed Sept. 12, 1946 4 Sheets-Sheet 2 I Lv45 2% LUGIEN LaCOSTE 3 ARNOLD RQMBERG INVENTORS ofiolh 5.6011 1? M ATT RNEYS March 18, 1952 LA COSTE ETAL 2,589,709

FORCE MEASURING DEVICE LUCIEN LaCOSTE ARNOLD ROMBERG INVENTORS A ORNEYS March 8, 1952 L. LA cosTE ETAL 2,589,709

FORCE MEASURING DEVICE Filed Sept. 12, 1946 4 Sheets-Sheet 4 FIG. 5

LUCIEN LaCOSTE ARNOLD ROMBERG INVENTORS BY I AT ORNEYS Patented Mar. 18, 1952 "UNITED STATES atEur OFFICE Lucien La Coste and Arnold 'Romberg,

' Austin, Tex.

Application September 12, 1:9 i6, Se rial No, 696,494

' This invention relates to improvements in measuring instruments which make it possible toobtain measurements whena steady base for the'injstrument is not accessible. It. is of particular importance in making underwater gravity meter measurements and .inmaking ordinary gravity meter measurements in marshy areas and .nearvolcanoes.

Y I hen adelicate measuring instrumentis placed np on an unsteady.base the readings are afiected,

and'particularly where the instrument has stops to prevent} excessive, movement of the balance member. Motions of the base cause-the balance memberto strike the stops and thereby introduce errors into the.imeadings. The present invention contemplates an arrangement of the instrument Whereby the frame which supports the balance member "may be moved relative to the instrument as a wholetwhen the balance member approaches the stopsand then the frame'can be returned to its initial position when the balance member moves away from the stop. In this manner there is not an excessive movement as between the balance member and the supporting frame, but the supporting frame is moved so as not to int ri wit t e Swing m e n o th balance member.-

Ap im'ar-y object of this invention is to obtain an underwater remote controlled gravity meter with; which gravity-measurements can be made in rough weather and on soft bottoms. A. second object is to obtain a gravitymeter with which gravity measurements can be made when" it is resting on asupport which undergoes earthquake motions or, motions similar thereto such as supports undergoin marshy land.

- A further object of the invention is to prevent the moving beam in the gravity meter from strike ing its limiting, stops when-'the-gravity meter support is accelerated a A-rstillfurther obj ect is to "counterbalance-large vaccelerations ofthe gravity meter support Jjby introducing additional counterbalancing accelerations. 1- 'An.'adiiitionalobject is to prevent such. addi- :tiunal counterbalancing accelerations from introducing errors :into the gravity measurements.

- Aiurther1object is to damp outrlarge initial kinetic energies that the gravity meter beam might have when it is firstreleased or "which it-might' acquire when-the meter is "badly jarred. The foregoing objects are primary objects and together with other objects will become' more apparent by reference-Ito the following descripnon-(andacconmanying drawings in which:

' Fig. l is a side elevation partly in sectionshow ing'the preferred form of the invention;

Fig.2 is a wiring diagram for the preferred form of the invention; Fig. 3. shows a form of the invention for man;- ual"operation;

t Fig. 4 is a wiring diagram for the formofthe invention of Fig. 3'; Fig. 5 is a side elevational view partly insectio'n showingthe invention applied to a torsion type gravity meter; and v Fig. 6 is a wiring diagram of. the averaging device used to obtain the average position of the gravitymeter beam.

In order to explore underwater andmarshy areas, attempts have been made to use gravity meters in underwater geophysical explorationby submerging them and allowingthe meter to rest on bottom. In these attempts, however, satisfactory results have been obtained only on very calm days and only on bottoms which were'not very soft. I v The importance of making a gravity meter for underwater use that can be employed on soft bottoms can'hardly be overemphasized because a complete gravity map cannot be obtained otherwise in manyregions. Furthermore, in view of the high cost of underwater gravity surveys it is extremely desirable that underwater gravity meters be capable of operation in weatherthat is not calm.

The failure of present underwater gravity meters to operate in iroughweather or on soft bottoms isdue to two diificulties: (1) water currents disturb thegravity meter, and (2) the bottom itself moves. The first of these difiiculties namely, water currents, can be sufiiciently re: duced by using a shield as described in our copending application, Serial Number 678,204,- filed June 21, 1946,.;on a Leveling Device, or by jetting the gravity meter under the bottom of the body of water, or by various other means.

- The second ,difi'iculty, namely, the motion of the bottom, can .be resolved into rotations, horie zontal translations, and vertical translations. The rotations are small and do not cause sub-'- stantial trouble.

.The horizontal'translations are sometimes large enough to cause the moving system of an ordinary gravity meter to strike the stops provided in the gravity .meter housing for limitingthe motionof the moving system. This motion must be kept small to avoid errors due to hysteresis in the gravity meter spring. However, considerable dam-ping for relative horizontal motion between the gravity meter housing and moving system can be provided without interfering with the operation of the gravity meter. This will prevent horizontal translations from causing the movable system to engage the stops.

Vertical translations, however, are also large enough to cause the movable system to strike the stops, but in this case the vertical damping in the gravity meter cannot be increased suificiently to prevent hitting the stops without seriously affecting the operation of the gravity meter. Any increased vertical spacing of the stops increases, errors due to hysteresis in the spring. supp rting beam l2 by the clamps 20. It is therefore clear 5 that the beam l2 will rotate about a horizontal axis under the influence of changes in gravity.

the moving system. Increased vertical damping increases the reading time to such an extent as to be prohibitive.

If the moving system of a gravity meter can be prevented from hitting the stops, a reading can be obtained by averaging the position of the movable system or gravity meter beam. A satisfactory electrical averager can be made for a good gravity meter. A diagram of such an averager is included in this disclosure. The real problem therefore, is to obtain a device which will prevent the gravity meter beam from hitting the vertical motion stops when the meter is subjected to vertical accelerations.

The present invention is a device for temporarily displacing the frame which supports the movable system so that during movement of the system it will not strike the frame. The displacing of the frame merely moves it out of the path of the moving system temporarily until the moving system starts back on its reverse swing and the frame is then returned to its initial position. Such displacement of the'frame avoids interference with the moving system so it does not affect the average beam position. Such movement of the frame prevents vertical translations of the ground from causing the beam to strike the stops by applying counterbalancing translations when the beam is near the stops. Obviously the'counterbalancing translations or displacement of the frame will introduce an error into the measurement of gravity unless their average acceleration duringthe time of taking a reading is negligible.

This condition is met by introducing suitable additional translations while the gravity meter beam is not near either the top or bottom stops on the frame. The method of doing this will be made clear by a study of the device itself.

In Fig. l the submersible portion l of a'rerhote control gravity meter is shown resting on the bottom 2 below a body of water 3. The submersible' portion I is shown as including a frame structure shown as a water-tight container 4 fixed Rotation of the beam I2 is limited by the lower stop 2| and the upper stop 22 both of which are fixed with respect to the inner housing It! in such a manner that the beam is limited in its movement to such an extent that the spring l3 will notbe subjected to appreciable hysteresis. The force of gravity on the beam is balanced by vertical adjustment of the clamp 18 to whichthe main spring I3 is clamped. This vertical adjustment is produced by turning the crank 23 of-the self synchronous generator 24 which is electrically connected through cable 25 to the self synchronous motor 26.

- The motor 26 turns as many revolutions as the generator 24. The shaft 21 of the motor 25 transmits rotation to the screw 28 through the gears 29, 30, 3|, and 32. The screw 28 is threaded in the inner housing It). The lower end of the screw 28 presses against the leaf spring l'|-. As the screw 28 moves downwardly the clamp l8 on the leaf spring moves downwardly by a smaller amount. The tension on the main spring l3 and therefore the equilibrium position of the beam I2 can therefore be adjusted by suitable rotation of'the crank 23 of the self synchronous generator 24 on the boat 33. Y Y A photoelectric cell system is used to give're-fmote indications of the position of the beam 12. The system includes an electric lamp 34 clamped in the bracket 35 which is fixed to the outer to leveling jacks 5 whose extensible members 6 j rest on the bottom 2 of the body of water. The 1 H detailed construction of such jacks is to be found our copending application Serial Number *"67.8,20'4, filed June 21, 1946, for Leveling Device. The container 4 is leveled by varying the position of the extension'members E.

In the container 4 is mounted a gravity meter 1; of the general type shown in our Patents Numhers-2,293,437 and 2,377,889.. A brief description' 66 of the gravity meter will first be given as an aid in describing the invention. Gravity meter details'to be described arenot necessarily those of theb'est gravity meter design, but instead are given-for simplicity. sincedetails of this nature are not a part, of this invention. Gravity meter details are given in our above patents.

The; gravity meter 1 includes a top plate 8, and outer housing 9 which are screwed together. The. inner housing In is fixed to the top plate 8 throu h housing 9. No source of potential for the lamp is shown. The lamp illuminates the slit- 36 in the bracket 35. Light from the illuminated slit strikes the mirror 31 which is also fixed to the bracket 35; the light is reflected to pass through the converging lens; 38 mounted on the inner housing [0. The light then is reflected from the mirror 39 fixed to the beam l2 and passes through the lens 38 again. The lens causes the light to converge and form an image 40 of the slit 36. I The image 40 falls on one or both cathodes 4| and 42 of the double photoelectric cell 43 which is clamped in the bracket 44 fixed to the outer housing 9. The position of the beam" l2 determines where the image falls with respect to the two cathodes 4| and 42. Generally the zero or reference position of the beam is taken as the position which causes equal amountsof light from the image to fall on' the two photo'- electric cell cathodes. The photoelectric cell 43 is electrically connected to the amplifier 45 through the cable 46. The amplifier gives a voltage output proportional to the difference in the two cathodes. Furthermore, the voltage output has one sign when the beam I2 is near'thetop stop. 22 and the other sign when the-beam is near the bottom sto 2|. Amplifiers capableof satisfying these conditions are well known in the 1 The. output of the amplifier is'delivered to the averager-fl. and to the relay unit 48 through the cables 49 -and. 59 respectively.whichextend to assowoe the boat 33. The averager isan amplifier with a time delay. Fig. 6 gives a circuit for an. aver ager; it will be described later. The time delay causes the meter 5I to give an average indication of the position of the beam I2. In actual practice a time delay of 10 seconds gave good results.

The properties and construction of the relay unit will be considered later.

The parts of the underwater gravity meter which have been described up to this point are suflicient to enable measurements of gravity to be made when there are not appreciable disturbances on the bottom of the body of water, that is, when the disturbances are not large enough to cause the beam I2 to strike the stops 2I- and 22 very often. Readings are taken by merely rotating the crank 23 until the meter 5I on the averager indicates its zero reading and noting the total angular displacement in revolutions and fractions thereof of the. crank from a predetermined reference position. The difference in gravity at two stations is proportional to the difference in angular. displacements of the crank required to obtain readings at. the two stations.

The present invention relates particularly'to the portions of the underwater gravity ,meter which eliminate the bumping of the beam'on the stops and will now be described. The top plate 8 of the frame of the gravity meter 1' has two vertical rods 52 fixed to it. These rods can slide freely inholes 53 in brackets 54 which are fixed to the watertight container 4. The outer housing or frame 9 is thereby capable of being translated or'displaced vertically relative to the container 4, but not horizontally. I

Predetermined amounts of vertical translation are made possible by means of the following construction. The Bakelite (or other heat insulating material) piece 55 is fixed to thecontainer 4. The ball bearing 60 fits into the hole BI in the piece 55. The shaft 52 fits in the ball bearing 60 and has a shoulder 63 which fits against the top of the inner race of the ball'bearing. The

ball bearing thus takes downward thrust exerted by the shaft 52.

A second bearing 64 for shaft 52 is provided by theplate 65 which is fixed to the piece 55 through the Bakelite blocks-66. A threaded portion 61 is provided on the upperv end of shaft 62. This threaded portion engages a nut'68 which is fixed to the outer housing 9 through the Bakelite spacer 69. A gear IO-is fixed to shaft 62. This gear engages gear 'II whichis fixed to counter-,

shaft 12. Thebevel gear 13 is also fixed to countershaft I2 and engages the bevel gear I4 which is fixed to the shaft I5 of the reversible electric motor I6. The electric motor is fixed to plate and is controlled from the relay unit 48 through the cable l1. From the preceding de-'- -'scription it can be seen that when the motor shaft I5 rotates, the outer lated vertically.

The cams I8 and 82 are fixed to shaft 92 and operate respectively the limit switch 19 and the switch 83. The cams and switches are better shown in Fig. 2. The relay unit 48 receives its inputs from the beam position amplifier, 45 and from the switches 79 and 83; its outputgoes' to the motor 16 which controls the vertical trans lation of housing 9. Fig. 2 shows a circuit diagram'of the relay-unit and its connections with other units of Fig. 1.

In Fig. 2 the-motor 16 is shown as having two series-fields 81 and 88. If current is sent through housingv 9 is transthe motor to be able to move housing 9 down-' wardly.

Relay 89 is controlled by cam I3and therefore serves as a lower limit relay for motion of housing 9. Similarlyrelay 90 is an upper limit relay for motion of housing 9. Lamps 'and BI are indicating lamps for indicating respec= tively when the lower and upper limits have been reached.

When the limit relays 89 and 90 are closed (neither limit being reached) the motor field lll is connected to contact of switch 83 and to contact 98 of relay 99. Also the motor field 89 is connected to contact 84 of switch 83 and to contact I00 of relay IOI. It is therefore apparcut that switch 83 can control the rotation of motor I5 if the contact arm I02 of switch '83 is at a positive potential and that relays 99 and IOI can control the rotation if the contact-arms I03 and I04 are at a positive potential. V Whether switch 83 or relays 99 and I0I control the motor is determined by the sensitiverelay I42. This relay is operated by the output of the beam position amplifier 45. The relay is adjusted so that when the beam I2 is near its lower stop 2I, the relay arm I43 touches the contact I 44. It is also adjusted so that when the earn. I2 is near its upper stop 22, the-relay arm I43 touches the contact I 05. The relay is also of such a type thatwhen the beam I2 is not near either stop, the arm I43 does not touch either contact; a relay ofthis type is the Weston Relay Model No. 534. )7 It is now apparent that when the beam I2 is not near either stop the double pole relay 93 :is not energized and a positivepotential is applied to switch 83,-but not to relays 99 and IOI. Under this condition switch 83 controls the motor 15. Switch 83, however, is controlled by cam 82 which moves in accordance with the vertical translation of the housing 9. When housing 9 isnear a predetermined reference position or zero po sition,'the-arm I02 of switch .83 doesnot touch either contact and the motor 10 stands still. When housing 9 is appreciably' below its zero position the-switch arm I02 touches contact; 84 which causes motor 16. to raise the housing; Sim ilarly if the housing is-appreciably above its zero position, the arm I02 will touch contact 85 and the housing will be lowered. It is therefore an: parent that if the beam I2 is not near either stop and. the housing 9is appreciably away from its zero position, then the motor 16 will operate to returnthehousing to its zero position. Let us now consider what happens when the beam I2 .moves close' to the lower stop 2|. When this, happens arm I43.o'f relay I42 touches contact I44 which energizes'both. relay 93 and'relay 99.1 The energizingiof relay 93 removesthe 8 volt positive potential from switch 83 and mi;- presses a 24 volt positive potential on the .contact arms I03 and I04 of relays 99 and II. The energizing of relay 9.! causes the relay arm I03 to touch the contact 98 which causes the motor 16 to lower the housing 9. Since stop. 2I is fixed to housing 9, this lowering moves the stopv away from thebeam'and prevents the beam from hitting it. In a similar way when the beam moves hearthe upper stop 22, relays 93 and H are caused to move back to its zero position. If the housingshould move to its lower or upper limiting positions, the motor will be prevented from moving it any farther from its zero position and. a lamp will indicate which limiting position has been reached. V l

The method of operation of the invention when a measurement of gravity is made will now be considered. To be specific let us assume that the gravitational torque on the beam I2 is considerably greater than the torque exerted by the spring l3. Under this condition the beam will spend more time near the lower stop 2| than near the upper stop 22. This will be indicated by a low indication on the meter 5| of the averager 41, and it will also result in the housing 9 being accelerated downwardly more than upwardly in order to prevent the beam from hjit ting the lower stop.

. y The low indicationof the averager will cause the operator to rotate the crank 23 to increase the tension in the spring l3. If, however, the operator does not increase the spring torque sufficiently to approximately equal the gravitational torque in a few minutes, the housing 9 will reach' its lowerlimit. The operator will find this outFby noting that the lamp 80 is lit. He will then'open switch l9! which will allow switch 83 in, the relay box to take control of the motor and bring 'the housing back to its zero position.

This procedure is repeated until the indication of the averager is brought near its zero value. The housing will then not reach its limitsfany more unless it just happens to be near alimit when the adjustment of spring tension is made approximately correct.

longer reaching its limits the adjustment of the With the housing. no

averager reading to zero can be made very simply.

It has been mentioned that only 3 volts isapplied to the motor 16 when it is controlledby switch 83 while 24 volts is applied to it when it is controlled by relays 99 and ID]. The purposeof this is to make the motor respond rapidly when the beam is approaching a stop, but to reduce the hunting to a minimum. An equal voltage or motor speed under both conditions is entirely satisfactory however. I The invention has been described in connection with a null reading gravity meter rather than with a deflection type of instrument. 0b-

fviiously it could be used with a deflection type of instrument. In this case the reading would be obtained from the averager rather than from the angular displacement of the crank 23 required to make the averager read zero. It is often more difficult, however, to get a good average with a deflection type of instrument because they are not generally as linear as the null instruments are.

Another form of the automatic embodiment of the invention is the following. It differs from the general preferred form just described. This form is incorporated in Fig. 2 in that the relay "I42 is adjusted so that'contact M4 is closed when til 8 is appreciably above its zero position. This adjustment will cause the motor 16 to operate to keep the beam very near its zero position; it will also prevent the returning switch 83 from controlling the motor except when switch I01 is opened.

The operation of this system is as follows. Assume that the gravitational torque is greater than the spring torque. The motor 16 will then have to accelerate the housing 9 downwardly in order to keep the beam l2 at its zero position. This will soon cause the housing to reach its lower limit, which will be indicated by the lighting of the lamp 89. The operator will then turn the crank 23 of the self synchronous generator 24 to increase the spring torque and will open the switch ill! to allow the housing 9 to return to its zero position. This procedure is then repeated until the housing reaches its upper limit. Successive approximations are then continued to bracket the correct adjustment more closely.

In this method although the correct adjustment is made, the housing 9 may still reach either its upper or lower limits. This can be seen as follows. Assume that the gravity meter is not subjected to any earthquake motions and that the spring torque is perfectlyadjusted for equilibrium, with the gravitational torque. It will be further assumed that the switch I0! is closed at the instant when the beam 12 is at its zero position, but moving toward the lowerstop with a considerable velocity. The relay I42 will then operate to cause the housing 9 to move downwardly with the same velocity. The beam will then remain perfectly balanced at its zero as long as housing 9 continues to move with the same velocity. But this will cause the housing to reach its lower limit. Similarly if the beam had been moving toward the upper stop instead of toward the lower stop at the instant switch I01 was closed, the housing would have reached its upper limit. 1 It should be pointed out'that the preferred form of the invention does not have this difficulty. Its operation under the previous conditions with the downward initial velocity are as follows. When the switch I0! is closed, the downward initial velocity of the beam l2 will carry it near the lower stop. In this process some of the initial downward velocity will be lost because of damping between the beam and housing 9; such damping is present in all gravity meters.

The relay contact 144 will then be closed and the housing 9 will be translated downwardly to prevent stop 2| from being hit. The beam will remain for some time near the lower stop. In this condition the torque exerted-by the spring l3 will exceed the gravitational torque exerted on the beam. This will cause the weighted end of the beam to be accelerated upwardly. The upward acceleration will soon give the weighted end of the beam an upward velocity. This upward velocity will carry the beam to a p sition near its upper stop and the damping resistance encountered in this motion will further reduce the velocity of the beam. If the beam still has enoughmomentum to carry it to the upper stop 22, the housing 9 will be translated upwardly to prevent the beam from hitting the stop. This type of oscillating movement will continue until the damping present in the gravity meter reduces its amplitude to an amount insuflicient to move the beam near the stops. The motor 16 will then no longer operate (if there is no earthquake moauser-e tion) and the damping will decrease-the oscilv lations to zero.

' A very simple modification ofthe invention indicated in Figs. 3 and 4. This Fig. 3 shows only the portions of this form of the invention which lie above the water surface because the portions which lie below the surface are exactly as shown in Fig.1.

- The tension on the gravity meter spring I3 is controlled by rotation of crank 23 exactly as in the preferred form of the invention. However,

in the simplified form of the invention no averager is shown; instead the output'of the beam position amplifier merely operates the electric respectively. This is shown in the wiring diagram of the simplified formof the invention shown in Fig. 4.v

Fig. 4 also shows that the switch 83 now merely axls are used in place of-vertical translations to prevent the beam from hittingits stops.

Fig. 6 shows a wiringdiagram of a satisfactory averager. The averager is merely an amplifier with a time delay in its input. The input is applied across the two equal resistors I32 and I33 in series in order to-obtain two equal input voltages for the two vacuum tubes Ill and H8. The large-capacity condensers H9 and I are connected respectively between the grid I2I and the cathode I23 through the cathode resistor I25 and'betweenthe grid'I22 and the cathode I24 through the cathode resistor I25. The signals ar'efapplied between the said grids and cathodes I and I3I.

tween the plates measures the input voltage.-

operates the lamps I99 and III] to indicate respectively when'the housing is below or above its zero position. The motor I6 is now controlled manually by the three position switch III.

The operation Of the simplified form of the invention is as follows. When the beam I2 approaches a stop, meter I08 indicates it and the observer controls motor 16 by operatin'g switch Ill to prevent the beam from hitting the stop. When the beam is not near either stop, the ob-f server looks at the lights I 09 and III) to determine which way to operate the motor to bring the housing back to its zeroposition. If the respectively through the high resistors I26 and 7 I21 and thereby a time delay or averaging is obtained because the condensers have to be charged through the resistors. The positive terminal of the B battery is connected to the plates I28 and I29 respectively through the plate resistors I 30 Th microammeter 5I connected be- Br'oadly this invention comprehends the application of controlled accelerations to the housings of measuring instruments in order-to counfectsbeing'measured.

si-The invention claimed is:

l. A gravity meter including a support, a weight, a spring suspending said weight from tera'ct or counter-balance disturbances in the efsaid support, means for accelerating said supayerag reading 0% meter I98 is low orv the hous ,ing 9 reaches its lower limit as shown by-lamp 80, the observer rotates the crank .23 to increase the spring tension in the gravity meter .and vice versa.

' The preceding operationis difiicult for an op.- erator but can be done under favorablecondi- I responding parts are numbered the same.- In

Fig. 5 is'rather similar to Fig. 1 andcor-= Fig. 5 however, the outer gravity meter housing 9 is mounted in the water tight container 4 in such a way as to permit rotation about a vertical axis rather than to permit vertical translation. This mounting is done as follows. The shaft H2 is fixed tothehousing 9 and rotates in the ball bearing II3 whose outer race is pressed into the block II4 which is fixed to the water tight container 4.

Similarly the shaft 62 is fixed to housing 9 and rotates in the ball bearing 60 which ,fits in the hole 61 in the Bakelite block "55. The Bakelite block is fixed to the container 4.. The shoulder 63. on shaft 62 rests on the inner race of ball bearing '60 and supports the weight of housing 9.

Housing 9 is rotated by the reversible electric motor 1a through the worm fixed to the motor-shaftv I5 and through theworm gearI I6 The operation of this form of the invention is' port to avoid interference with'the movement'of saidjfweight, and means for averaging the displacement of the weight relative to "the support. 1925 A gravity meter including a support, a weight, a spring suspending said weight from said support, and means for accelerating said support as a function both of'the movement. 'of' the" support and of the movement of said weight relative-to the support. J

. "3: An instrument for-making measurements where a steady base therefor is not accessible, including a support, a moving'system supported bysaid' support, means for temporarily displacing said support, means for indicating such displacementof said'support so as to compensate therefore-in determining the instrument readings; and additional means for averaging the displacement of the movable element relative to the support. I it A gravity meter including a support, a weight, aspring suspending the weight from-the support, means operable when the weightexceeds a predetermined displacement from a predetermined zero'position with respect to the support to in turn displace thesupport to limit said-I, displacement relative to said support, the said means also being operable when the predetermined displacement is not exceeded to return the support'to a. second predetermined zero position, means for averaging the displacement ofthe weight fromthe first zero position, and

means indicating when the support has exceeded second a second predetermined displacement from. the

zero position. gravity meter including a support, a

V weight; a spring suspending the, weight from the supp rt, a case, means operable when the weight ex eeds a predetermined displacement froina predetermined zero positionvwith respectto the sup prt. to accelerate the support with respect 31159} dis placment is not exceeded to return the suptofi tlri. case to limit the displacement offjthe wei ght relative to the support, the said means being operable when said predetermined to give the support a vertical acceleration to limit said displacement of the weight relative to the support, the said means also being operable when the predetermined displacement is not exceeded to return the support to a second predetermined zero position, means for averaging the displacement of the weight from the first zero position, and means indicating when the support has exceeded a second predetermined displacement from the second zero position.

7. A gravity meter including, a support, a weight, a spring suspending the weight from the support, said weight being adapted to rotate about a vertical axis under the influence of variations in gravity, means operable when the weight exceeds a predetermined angular displacemen from a predetermined zero position with respect to the support to give the support an angular acceleration about a vertical axis to limit said angular displacement relative to said weight, the said means also being operable when the prede termined angular displacement is not exceeded to return the supportto a second zero position, means for averaging the angular displacement of the weight from the first zero position, and means indicating when the support has exceeded a second predetermined angular displacement from the second zero position.

8. A force measuring instrument comprising, a support, a force responsive element, means supporting said element to move in response to variations in the force being measured, and means for displacing said support to avoid interference with the movement of the element, and means for averaging the displacement ofthe force responsive element relative to the support. 9. A force measuring instrument including, 'a support, a movable element adapted to move in response to a force being measured, means for displacing said support in a direction to avoid interference with the movement of said element,-

and means for averaging the displacement of the movable element relative to the support.

10. The method of making measurement with a force measuring instrument having a support and a moving system thereon responsive to the force to be measured comprising the steps of,

, engagement of the support and system has passed.

11. The method of making measurementswith a force measuring instrument having a support, and a moving system thereon responsive tothe.

force to be measured comprising the steps'of, moving the support of the instrument in direction to avoid interengagement of the system,

with the support due to relative movement therebetween, returning the support to a predetermined reference position when danger of interengagement of the support and system have passed, and simultaneously averaging the relative position of the moving system and support.

12. The method of making measurements with a force measuring instrument having a, support and a moving system thereon responsive to the force to be measured comprising the steps of, moving the support of the instrument in a direction to avoid interference with movement of the system, measuring the displacement of the moving system from a predetermined zero position, and simultaneously averaging the relative position of the moving systemfland the support.

13. A gravity meter comprising a frame structure, a support adjustably carried by the frame structure, power means'lfor adjusting said support on said frame structure, a gravity responsive means including means yieldably suspending a weight from said support, means for sensing movement of said gravity means in excess of a. predetermined limit relative to the support, and means connecting said sensing means to said power means to cause said power adjusting means to displace said support in a direction to limit the movement of said gravity means relative to said support. p a

14. A gravity meter comprising a frame structure, a support adjustably carried by the frame structure, power means for adjusting said support on said frame structure, a gravity responsive means including a spring suspending a weight from the support, means for sensing move-,

ment of said gravity means in excess of a pre-' determined limit relative to the support, and means connecting said sensing means to said power means to cause said power adjusting means recited in claim 14 16. A force measuring instrument including;

a movable element adapted to move in response toa force being measured, a support therefor,

means, responsive to excess relative movement between the force responsive element and the support, for displacing said support in a direction toavoid interference with the movement of said element, and mean for averaging the displacement of the movable element relative to the support.

LUCIEN LA COSTE.

ARNOLD ROMBERG.

REFERENCES CITED The following references are of record in the file of this patent:

-UNITED STATES PATENTS Number Name Date- 1,35035 Clarke Aug. 24, 1920 1,921,983 Wittkuhns Aug. '8, 1933 1,930,945 Sjostrand Oct. 17, 1933 2,253,472 Pepper Aug. 19, 1941 2,362,135 James Nov. '7, 1944 James Jan. 9,1945

OTHER REFERENCES Ser. No. 297,006, SteineniiA. P. 0.), published -May 25, 1943.

comprises a water- 

